1. Field of the Invention
The present invention relates to an elevator apparatus, and particularly, to an elevator apparatus having a detector for detecting the position of a car.
2. Description of the Related Art
One form of art for detecting the position of an elevator car is disclosed in U.S. Pat. No. 5,052,522. In this art, a roller is kept in contact with a rotary portion, such as an idler sheave, of an elevator hoist constituting a part of the drive system, so as to drive a position detector.
In another form, a position detector is driven by utilizing the rotation of a governor (Japanese Patent Unexamined Publication No. 3-177283).
In the former art, since the idler sheave is driven by the main rope by which the car is suspended, wire-lubricating oil contained in the main rope may bleed to the surface of the idler sheave on which the roller of the position detector rolls, and thus cause adhesion of dust to the sheave surface. As a result, the roller may slip on the sheave surface, or may have to run on dust adhered to and deposited on the sheave surface, thereby making it impossible to effect accurate detection of position. In order to avoid this problem, an arrangement is disclosed, for example, in Japanese Patent Unexamined Publication No. 62-27283, in which the roller of the position detector rolls on the outer peripheral surface of a brake drum which surface is free from influence by lubricating oil on the rope. With this arrangement, however, since the brake drum is provided in the drive system, accurate position-detection is impossible when there is slip between the drive system and the main rope. Actually, therefore, the adoption of the arrangement is combined with the use of another position detector.
In the latter art, the rotary shaft of the position detector is directly connected mechanically with the rotary shaft of the governor. It is difficult to effect connection in such a manner as to achieve alignment between the axis of rotation of the position detector, which is a precision instrument, and the axis of rotation of the governor. As a result, when there is a deviation in the axis of rotation, it is difficult to effect precise position-detection. Another drawback is that no consideration is given to an arrangement for increasing the number of pulses generated for position detection so that it is not readily possible to effect accurate position-detection.